1. Field of the Invention
This invention concerns cam actuation clutch or brake devices and more particularly electromagnetic clutching arrangements including a camming ball-recess combination in which the torque transmitted through the clutch is exerted on the ball so that the camming forces increase with increasing torque levels. The camming force increases the engagement force of an armature moved into engagement by an electromagnetic coil.
2. Description of the Prior Art
In copending application Ser. No. 686,854 filed May 17, 1976, there is disclosed an electromagnetic coil operated clutch in which an armature is axially moved into engagement with radially spaced pole faces formed on an input member inner body upon energization of an electromagnetic coil. The armature is drivingly connected to the output member by means of a plurality of balls disposed in conical recesses within the armature and on an opposing radial face formed on the output member. The camming action of the balls in the recesses, upon engagement of the armature with the input member, locks up the clutch, and the balls themselves transmit the maximum torque from the armature into the output member. This arrangement produces an extremely rapid action but the transmission of torque by the balls tend to limit the torque levels which can be safely and reliably transmitted. This is due to variations in the recess geometry produced in manufacturing and variations in the frictional coefficients which may produce failures to release at high torque levels due to jamming of the balls or damage to the components such as tearing of the pole faces.
It is the object of the present invention to provide such a clutch in which the maximum torque is transmitted through balls, but in which the camming action is torque limited to allow the transmission of relatively high torque levels without the danger of jamming lock-up.